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package model.sessionBeans;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import java.util.List;


/**
 *
 * @author maged.abdelmoeti
 */
public class SuperSessionBean<T> {

    @PersistenceContext(unitName = "TestPU")
    private EntityManager em;

    public SuperSessionBean() {
    }

    public EntityManager getEntityManager() {
        return em;
    }
       
        private Class<T> entityClass;

        public SuperSessionBean(Class<T> entityClass) {
            this.entityClass = entityClass;
        }

       // protected abstract EntityManager getEntityManager();

        public void create(T entity) {
            getEntityManager().persist(entity);
        }

        public void edit(T entity) {
            getEntityManager().merge(entity);
        }

        public void remove(T entity) {
            getEntityManager().remove(getEntityManager().merge(entity));
        }

        public T find(Object id) {
            return getEntityManager().find(entityClass, id);
        }

        public List<T> findAll() {
            javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
            cq.select(cq.from(entityClass));
            return getEntityManager().createQuery(cq).getResultList();
        }

        public List<T> findRange(int[] range) {
            javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
            cq.select(cq.from(entityClass));
            javax.persistence.Query q = getEntityManager().createQuery(cq);
            q.setMaxResults(range[1] - range[0]);
            q.setFirstResult(range[0]);
            return q.getResultList();
        }

        public int count() {
            javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
            javax.persistence.criteria.Root<T> rt = cq.from(entityClass);
            cq.select(getEntityManager().getCriteriaBuilder().count(rt));
            javax.persistence.Query q = getEntityManager().createQuery(cq);
            return ((Long) q.getSingleResult()).intValue();
        }
        

}
